The invention relates to an unwinding apparatus for a paper or board web or the like for use with a succeeding rewind station, such as a two drum winder, a single drum winder, or the like.
Such an unwinding apparatus is known from U.S. Pat. No. 3,327,959. On it, an expiring winding roll (empty spool) is exchanged for a new, full roll (parent roll) while the web is being pulled off the winding roll at reduced speed. In the process the expiring roll is lifted out of the unwinding position and the new parent roll is conveyed out of its waiting position into the unwinding position. The web continuing to be unwound from the roll in the new position is led around a cross member designed as a guide roll, which extends close along the periphery of the new parent roll in the unwinding position. The new web- beginning on the parent roll is given an application of adhesive to attach the beginning of the web to the expiring web of the empty spool. For this purpose the peripheral speed of the parent roll must be matched to that of the unwinding web. Shortly before the web material on the spool has been fully unwound, the guide roll is swung against the periphery of the new, rotating parent roll in order to bring the end of the unwound web in contact with the splicing point of the parent roll. When the splice has been made, a separating device separates the expiring web, which carries the beginning of the web along onto the new parent roll. The empty spool is now lifted out of its position and deposited in a storage means out of which it can be taken with a hoist.
To be capable of performing such an exchange of the empty spool for the new parent roll, the known unwinding device involves a relatively expensive design: guideways and drive means must be prepared to convey the expiring roll out of the unwinding position. The succeeding new parent roll brought into the unwinding position is synchronized by means of a drive with the speed of the unwound web. Furthermore, a sophisticated machine control system is provided to perform the splicing operation. Nevertheless, with the known device, uncontrolled web doublings of different lengths occur during the splicing operation, which may lead to troubles with the subsequent processing of the web.
In the case of winding machines in which, for example, after a longitudinal slit of the unwound web, the web is wound up on two drums or single drums into rolls which are relatively large in diameter, it is necessary, on completion of these rolls, to stop the machine so that the rolls can be taken out of the machine. Completion of the rolls is arranged in such a way that during such a stop an empty spool can be exchanged for a new parent roll. The time advantage obtained with the aforementioned known unwinding apparatus decreases, however, quite considerably during the exchange of the empty spool for a parent roll.
A winding machine with an unwinding apparatus is known from German Patent Publication No. 34 40 107, with which, towards the end of the unwinding operation, a certain web length is stored in a web length storage means during machine shutdown and subsequently the web is separated. The stored web length is then wound up on a suction roll arranged parallel to the roll axis. The empty spool is thereafter lowered out of the unwinding apparatus with a conveyor, and when it has been transported away, a new parent roll is lifted into the unwinding position.
The suction roll is subsequently pressed against the periphery of the new parent roll and the web-end section on the suction roll unwound with simultaneous slow turning of the roll. Adhesive is then applied to the web-end at the periphery of the new parent roll, resulting in the end of the web being attached to the beginning of the new web, with inadmissibly long doublings of the web in the area of attachment being avoided by appropriate control of the suction roll and the winding roll drive. This control complicates the unwinding apparatus, since parent rolls with differing diameters have to be processed. In addition, drive means are required for rewinding the separated end portion of the web. Winding and unwinding of the web portion delays the changing operation of an empty spool for a new parent roll, as well as the consecutive separation of the web and depositing of the empty spool out of the unwinding apparatus. Furthermore, vertical transport of the rolls is disadvantageous, since a new winding roll can be supplied to the unwinding apparatus only after delivery of the empty spool from the handling equipment.
In addition, an unwinding apparatus designed for a "flying splice" is known from U.S. Pat. No. 4,173,314, with which a drive unit drives a parent roll provided with an application of adhesive around the periphery and an expiring winding roll with the same peripheral speed. An oscillating roll dipping into the drawn-off web is used to control the drive unit. In addition, a splicing unit is provided, which has no contact with the web in its neutral position. As the winding roll expires, a mark arranged on the end face at the parent roll, which stands in relation to the application of adhesive, triggers a swivelling movement of the splicing unit, so that the web is separated and the formed web-end is simultaneously attached to the parent roll.
On the other hand, U.S. Pat. No. 4,575,016 shows an unwinding apparatus on which the splicing operation takes place with the new winding roll at rest. Prior to this, however, the web is brought into a web length storage means in considerable length, so that the web can be withdrawn from the storage means during splicing and does not need to be interrupted. The web unwound from the virtually empty spool is firmly clamped to a splicing unit, separated and placed in a position in which the formed web-end is provided with an application of adhesive. Following this, the empty spool is removed and a new spool put in its place in a well-defined position. The splicing unit now presses the web-end against the beginning of the web at the periphery of the new spool. After attachment of the webs the clamp is removed and the splicing unit led away from the spool.